1. Field
Example embodiments relate to a ferrocene-containing conductive polymer, an organic active layer including the conductive polymer, an organic memory device including the organic active layer and methods for fabricating the organic active layer and the organic memory device. Other example embodiments relate to a ferrocene-containing conductive polymer including a fluorenyl repeating unit, a thienyl repeating unit and a diarylferrocenyl repeating unit, an organic active layer including the conductive polymer, an organic memory device with improved operating characteristics and improved non-volatility fabricated using the organic active layer, and methods for fabricating the organic active layer and the organic memory device.
2. Description of the Related Art
With the recent dramatic developments in digital communication technology, demand for a variety of memory devices has been increasing rapidly. As the use of portable computers and electronic devices, including mobile terminals, smart cards, electronic money, digital cameras, personal digital assistants, digital audio players, multimedia players and others, has been extended in recent years, memory devices for use in these portable computers and electronic devices are required for retaining data in memory even when no power is being applied to the memory device, thereby tending to reduce the memory-related power consumption of the device.
Conventional memory devices may include a bistable element that may be switched between a higher resistance state and a lower resistance state when a voltage is applied to the devices. Resistive memory devices may be memories whose resistance is varied depending on an applied voltage and in which data may be stored in response to variations in the resistance.
Chalcogenide materials, semiconductors and various types of oxides and nitrides may be known to have resistive memory properties. Some organic materials may also be found to have resistive memory properties. Of these resistive memory devices, organic memory devices may include an upper electrode, a lower electrode and a memory layer between the upper and lower electrodes to utilize the bistability of resistance values obtained when a voltage is applied between the upper and lower electrodes for storing data. Such organic memory devices have attracted increasing attention as next-generation memories because they provide the desired non-volatility, which is an advantage associated with conventional flash memories, while also providing improved processability, reducing fabrication costs and/or improving the degree of integration.
One example of such an organic memory utilizes a 7,7,8,8-tetracyano-p-quinodimethane (CuTCNQ), which is an organometallic charge transfer complex compound, as the organic material. Another example includes semiconductor devices comprising an upper electrode, a lower electrode and an intermediate layer between the lower and upper electrodes, wherein the intermediate layer is formed from a mixture of an ionic salt, e.g., NaCl or CsCl, and a conductive polymer.
Other work has suggested organic memory devices comprising organic active layers and a metal nanocluster applied between the organic active layers, but efforts in this area have been hampered by relatively low yields, difficulties in forming suitable metal nanoclusters and reset voltages of about 0 V, rendering such devices generally unsuitable for widespread use as a nonvolatile organic memory.
Various materials have been investigated due to their potential use as materials for organic active layers of organic memory devices. One example of such an organic memory device may include an upper electrode, a lower electrode and a selectively conductive media between the two electrodes, wherein the selectively conductive media contains an organic layer and a passive layer and the organic layer may be comprised of a conjugated organic material.
Metallocenes and their derivatives are currently being investigated for their inherent electrical, optical and magnetic properties, for example, their ability to be oxidized to form mixed valent states. A major portion of research on metallocenes and their derivatives has been devoted to their use as fuel additives and polymerization catalysts. However, no study on the use of metallocenes and their derivatives as materials for active layers of organic memory devices has been reported.